Dissociation Constant Given Enzyme Substrate Complex Concentration Calculator

Formula Used:

\[ K_i = \frac{I}{\left(\frac{\left(\frac{[E_0] \times S}{ES} - S\right)}{K_M} - 1\right)} \]

Inhibitor Concentration (I):

mol/m³

Initial Enzyme Concentration ([E₀]):

mol/m³

Substrate Concentration (S):

mol/m³

Enzyme Substrate Complex Concentration (ES):

mol/m³

Michaelis Constant (Kₘ):

mol/m³

Enzyme Inhibitor Dissociation Constant (Kᵢ):

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1. What is Enzyme Inhibitor Dissociation Constant?

The Enzyme Inhibitor Dissociation Constant (Kᵢ) is a measure of the affinity between an enzyme and its inhibitor. It represents the concentration of inhibitor required to occupy half of the enzyme's active sites in the absence of substrate.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ K_i = \frac{I}{\left(\frac{\left(\frac{[E_0] \times S}{ES} - S\right)}{K_M} - 1\right)} \]

Where:

\( K_i \) — Enzyme Inhibitor Dissociation Constant (mol/m³)
\( I \) — Inhibitor Concentration (mol/m³)
\( [E_0] \) — Initial Enzyme Concentration (mol/m³)
\( S \) — Substrate Concentration (mol/m³)
\( ES \) — Enzyme Substrate Complex Concentration (mol/m³)
\( K_M \) — Michaelis Constant (mol/m³)

Explanation: This formula calculates the dissociation constant by relating inhibitor concentration to the enzyme-substrate complex formation and Michaelis-Menten kinetics.

3. Importance of Dissociation Constant Calculation

Details: The dissociation constant is crucial for understanding enzyme inhibition mechanisms, drug design, and determining the potency of enzyme inhibitors in biochemical and pharmacological studies.

4. Using the Calculator

Tips: Enter all concentration values in mol/m³. Ensure all values are positive and the enzyme-substrate complex concentration is less than or equal to the initial enzyme concentration.

5. Frequently Asked Questions (FAQ)

Q1: What does a lower Kᵢ value indicate?
A: A lower Kᵢ value indicates stronger inhibitor binding affinity to the enzyme, meaning the inhibitor is more potent.

Q2: How is Kᵢ different from Kₘ?
A: Kₘ is the Michaelis constant representing substrate affinity, while Kᵢ represents inhibitor affinity to the enzyme.

Q3: What are typical units for Kᵢ?
A: Kᵢ is typically expressed in concentration units such as mol/m³, M (molar), or mM (millimolar).

Q4: When is this calculation most useful?
A: This calculation is particularly useful in enzyme kinetics studies and drug discovery research where quantifying inhibitor potency is essential.

Q5: What are limitations of this calculation?
A: The calculation assumes ideal conditions and may not account for allosteric effects, multiple binding sites, or non-competitive inhibition mechanisms.